Presentation A Multitudinous Development of Microbeam Radiation Research in Japan

Matsumoto, Hideki  ,  Tomita, Masanori  ,  Maeda, Munetoshi  ,  hatashita, Masanori  ,  Funayama, Tomoo  ,  Yokota, Yuichiro  ,  Kobayashi, Yasuhiko  ,  Hirayama, Ryoichi  ,  Konishi, Teruaki

A classic paradigm in radiation biology asserts that all radiation effects on cells, tissues and organisms are due to the direct action of radiation on living them. According to this model, possible risks from exposure to low dose ionizing radiation (below 100 mSv) are estimated by extrapolating from data obtained after exposure to higher doses of radiation, using a linear non-threshold model (LNT model). Although this model is applied carefully and conservatively, there is room for concern about the validity of the low dose exposure risks obtained in this way because a number of findings have accumulated which cannot be explained by the classical target theory of radiation biology. Specific cellular responses observed in response to low dose and/or low dose-rate radiation have been described as the radioadaptive response, the radiation-induced bystander response, low-dose hyper-radiosensitivity, and genomic instability. All of these phenomena are considered to be responses to radiation which involve non-targeted molecules or molecules which have not interacted directly with radiation.Over the past dozen years or so, several microbeam irradiation facilities were built in Japan, which turned the radiation biological studies regarding cellular responses to low dose/low dose rate radiation using them into a beehive of activity in Japan. The microbeam irradiation facilities, which are communally available, are currently installed in four institutes in Japan. Firstly, in Japan Atomic Energy Agency, Takasaki, the irradiation experiment to mammalian cells using heavy ion microbeams was initiated in 1995. Subsequently, in High Energy Accelerator Research Organization, Tsukuba, the irradiation experiment using synchrotron X-ray microbeams was initiated in 2003. Thereafter, the microbeam irradiation experiments were successively started in Central Research Institute of Electric Power Industry, Tokyo and National Institute of Radiological Sciences, Chiba from 2007 and 2008, respectively.In the present talk, we will introduce the development of findings regarding cellular responses against radiation, which involve radioadaptive response, bystander response, low-dose hyper-radiosensitivity, and genomic instability, using the microbeam irradiation facilities in Japan.
15th International Congress of Radiation Research

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